1. Field of the Invention
The present invention relates to a light source, and more particularly to a broadband light source capable of generating light over a wide wavelength range.
2. Description of the Related Art
Since a wavelength division multiplexed optical communication system widely used recently is an optical communication system for transmitting a plurality of channels of different wavelengths, each containing data, the system must include a plurality of optical devices such as optical transmission means for transmitting each of the channels and optical detection means for detecting respective optical signals having different wavelengths.
The optical devices constituting the wavelength division multiplexed optical communication system require a broadband light source for generating light over a wide wavelength range as means for testing their optical performance and characteristics. Herein, the broadband light source may be also used in generating light over a wide wavelength range for inducing a mode-lock of each Fabry-Perot laser for generating the channels.
A rare-earth doped fiber amplifier capable of generating a spontaneous emission light having a predetermined wavelength band, or a semiconductor optical amplifier may be used as the broadband light source. However, since the broadband light source has low output power, its use is limited.
FIG. 1 is a view showing a construction of a conventional broadband light source. Referring to FIG. 1, the conventional multi-wavelength light source includes a first amplifying medium 110, a second amplifying medium 120, a first pumping means 140 for pumping a first pumping light to the first amplifying medium 110, a second pumping means 150 for pumping a second pumping light to the second amplifying medium 120, a first isolator 101 located between the first and the second amplifying mediums 110 and 120, a second isolator 102, and a reflector 130.
The first amplifying medium 110 outputs an L-band spontaneous emission light at both sides, and amplifies the L-band spontaneous emission light reflected by the reflector 130 to output the amplified spontaneous emission light to the first isolator 101.
The first pumping means 140 includes a first pump light source 142 for generating the first pumping light for pumping the first amplifying medium 110, and a first wavelength selective coupler 141 for outputting the first pumping light generated from the first pump light source to the first amplifying medium.
The first wavelength selective coupler 141 is located between the reflector 130 and the first amplifying medium 110 in order to output the L-band spontaneous emission light generated from the first amplifying medium to the reflector and to output the L-band spontaneous emission light reflected by the reflector to the first amplifying medium.
The second pumping means 150 includes a second pump light source 152 for generating the second pumping light, and a second wavelength selective coupler 151 for outputting the second pumping light generated from the second pump light source to the second amplifying medium 120.
The second pump light source 152 outputs the second pumping light for pumping the second amplifying medium 120 to the second wavelengths elective coupler 151 and may employ a photo diode.
The second wavelength selective coupler 151 outputs L-band and C-band spontaneous emission lights, which are outputted from the second amplifying medium 120, to the second isolator 102.
The second amplifying medium 120 is pumped by the second pumping light to generate the C-band spontaneous emission light, and amplifies the L-band spontaneous emission light inputted from the first isolator 101 to output the amplified spontaneous emission light to the second wavelength selective coupler 151.
The second isolator 102 outputs the L-band and C-band spontaneous emission lights to an exterior of the broadband light source through an output terminal ‘Output’, and blocks light progressing in reverse from the output terminal ‘Output’ to the second amplifying medium 120.
In the conventional broadband light source, the first amplifying medium amplifies the L-band spontaneous emission light reflected by the reflector, and the second amplifying medium amplifies again the L-band spontaneous emission light amplified by the first amplifying medium. Therefore, the broadband light source has high amplification efficiency for the L-band spontaneous emission light.
However, the conventional reflector cannot simultaneously have a wide wavelength band and a high reflection factor.